Prediction of inundation due to Kabuyanda dam failure and its impact on the communities of Isingiro district, western Uganda

Abstract

Globally, dams are indispensable in overcoming hindrances posed by climate change through ensuring sustainable water supply for irrigation. However, in case of failure, Dam floods cause devastating effects in fatalities and financial losses. The study focused on predicting the flood extent in case of Kabuyanda dam failure, determining the exposure of land use types, estimate the damages/losses resulting from the inundation in the eventuality of the dam failure and establish possible flood mitigation measures in Isingiro district. A cross-sectional survey design was adopted following both qualitative and quantitative approaches. Hydrologic Engineering Center River Analysis System model was used to predict flow simulation while depth-damage stage, and replacement values were considered for risk analysis. The data used was acquired from Uganda Beareau of statistics, Ministry of education and sports, Ministry of health, Ministry of water and environment, National risk and vulnerability atlas for Uganda, key informant interviews, and google earth. Geo-spatial analysis, descriptive statistics, and Nvivo software were used to analyze the data. The study revealed that in the eventuality of a dam failure, the spatial extent of floodwater would inundate approximately 1,745.65 hectares of land totaling 43.20% of the Kabuyanda flood plain (4040.60 hectares) with flood velocity and depth ranging between 11.99 m/s to 0 m/s and 0-8.4 m respectively. About 5, 756 people, 319.15 hectares of croplands, 178 roads, 8 schools, police post, and a medical center are exposed to potential dam-break inundation and damage with loss estimate totaling approximately 4,158,130,546 UGS. Flood preparedness will be more vital than response and recovery. Low flood zone and uphill regions are suggested as evacuation centers; river banks for forestry and flood fringe for crop cultivation. Conclusively, elevation within the flood plain determines water surface movement, damageability while losses depend on flood velocity and depth. Therefore, flood emergency preparedness strategies are a prerequisite in protecting the downstream population, reducing the damages and losses that could to result from potential dam failure. The estimated cost is 1,670,738 USD (5,912.992,392 UGX) towards meeting the activities to mitigate an inundation disaster in Kabuyanda irrigation scheme in the Isingiro notably evacuation and resettlement from the flood danger spots.